Fluid burner safety control apparatus with ignition timing



May 4, 1948. J. o. ROSCHE 2,440,700

I FLUID BURNER SAFETY CONTROL APPARATUS WITH IGNITION TIIING Filed Aug. 3, 1945 fll' INVENTOR.

JOHN 0. #05 0115 Patented May 4, 1948 UNITED STATES PATENT OFFICE FLUID BURNER SAFETY CONTROL APPARA- TUS WITH IGNITION TIMING John 0. Rosche, Minneapolis, Minn., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation oi. Delaware Application August a, 1945, Serial No. 608,751

. 8 Claims. 1

The present invention is concerned with a fluid fuel burner control apparatus and more particularly with apparatus of the type employing a timerto control certain functions. This application is a continuation in part of my copending application Serial No. 607,631, filed July-28, 1945.

An object of the present invention is to provide an improved burner control system in which a single timer is employed to both time an opera-- tion of the blower following the interruption of fuel delivery after a termination of a call for heat and to provide for a safety shut down at the end of a predetermined period of time if combustion is not successfully established.

A still further object of the present invention is to provide such an arrangement in which the timer also functions to time the ignition period.

A still further object of the present invention is to provide such an arrangement in which provision is made if desired for operation of an oil preheater.

A still further, object of the present invention is to provide such an arrangement in which the I timer is a thermal timer which operates to provide either of two ignition timing periods and a timing period of different length for the operation of the blower following the interruption offuel.

A further object of the present invention is to provide such an arrangement in which provision is made for delaying the opening of the fuel oil valve after the operation of the blower.

Other objects of the invention will be apparent from a consideration of the accompanying specification, claims, and drawing, of which Figure 1 is a schematic showing of the improved burner control apparatus associated with portions of the burner apparatus being controlled,

Figure 2 is a schematic view of one relay employed in the apparatus, and

Figure 3 is a schematic view of another relay employed in my apparatus.

Referring to Figure 1, the burner apparatus to be controlled comprises a blower l employed to supply air under pressure to an atomizing type of oil burner, the nozzle of which is shown in the lower part of the figure and designated by the numeral 14. The numeral II is employed to indicate an oil valve which controls the flow of fuel to the burner. This valve may, for example, be of a solenoid type whichis open whenever ener- 2 burner whenever gas is supplied thereto. This means might well be an electrical ignition means which is energized simultaneously with the pilot burner gas valve. ignition means is not shown. An electrical heater I5 is employed for preheating the oil before it is delivered to the burner. The operation of this heater is. controlled by a thermostat 2| havj with two contacts I9 and 20. As indicated by the Q legend adjacent the thermostat, the bimetallic gized and closed when deenergized. Also included in the burner apparatus being controlled I is a pilot burner gas valve l2 which controls flow of fuel to a pilot burner l3. Provided with the element ll moves contact arm I! to the left upon a drop in temperature. The contact arm 18 is so spaced from contacts l9 and 20 that it first engages contact l9 and then upon a further drop in temperature engages contact 20.

The thermostat I6 controls the energization of a relay indicated in its entirety by the reference numeral 25. This relay comprises a relay coil 25a and a plurality of switch blades 25b, 25c, 25d,

25c, 25], and 25g. In order to simplify the showing of the circuit, switch blades 25 and 259' have been shown in a different portion of Figure 1 than switch blades 25b, 25c, 25d, and 25a. illustrate the normal relationship between the units of relay 25, the relay has been shown with the elements in their normal relation in Figure 2. The relay switch blades 25b, 25c, 25d, 25f, and 259 are biased out of engagement with contacts 25h, 25k, 25m, 2511, and 25p, respectively, and are moved into engagement with those contacts upon energization of relay coil 25a. Switch blades 25c and 25e are biased into engagement with contacts 25s and 25f and are moved out of engagement with these contacts upon energizatlon of the relay coil 25a. The reference numeral 40 is employed to generally designate a further relay. This relay comprises a coil 40a and four switch blades 40b, 40c, 40d, and Mic. The latter switch blade is shown in the upper portion of the drawing to simplify the showing of the circuit. The relay is shown with the elements thereof in their normal relationship in Figure 3. The switch blades For purposes of simplicity, this In order to 48b, 48c, 48d, and 48e cooperate with fixed contacts 48f, 48g,48h, and 48k. The blades 48d and 48e are normally biased into engagement with contacts 48; and 4810, respectively, being moved out of engagement therewith upon energization of the relay coil 48a. The switch blades 48c and 48d are biased out ofengagement with flxed contacts 48g and 48h, being moved into engagement with these contacts upon energization of relay coil 48a.

The relay 48 is controlled by a flame responsive apparatus including an electronic discharge tube 58. This tube comprises an anode 5|, a grid 52, and a cathode 53. Associated with the cathode is a cathode heater 54. The three electrodes together with the cathode heater are enclosed in an envelope 55 which may, for example, be evacuated. The tube 58 is supplied with power by a transformer 59, this transformer comprising a primary winding 88, a high voltage centertapped secondary winding 6|, and a. low voltage secondary winding 62. The secondary winding 62 is connected by conductors 83 and 84 to the filament heater 54. The extreme right hand terminal of secondary BI is connected to relay winding 48a which in turn is connected by conductor 85 to anode 5|. The center tapped secondary BI is connected by conductors 58 and 61 to the cathode 53. Thus, the right hand side of secondary BI is employed as a source of plate potential for the anode circuit of tube 58.

The left hand side of secondary GI is employed to control the potential of grid 52. The extreme left hand end of secondary 6| is connected to grid 52 by conductors 58 and 89, resistor 18, condenser 1I, conductors 12 and 13, and resistor 14. A further resistor 15 and a further condenser 16 are connected between conductor 61 leading to the cathode 53 and conductor 13 leadin to the grid 52. Since condenser 16 and resistor 15 are connected between the grid and cathode,

' the voltage across these members largely determines the voltage applied to grid 52. As will be explained more fully later, an alternating voltage is normally impressed across condenser 16, this alternating voltage being 188 out of phase with the voltage applied to anode 5I.- Connected in parallel with resistor 18 and condenser H are two flame detecting devices each designed to respond to a different flame and each having a rectifying characteristic when exposed to a flame. be associated with the pilot burner I3 is a flame electrode 88 which is connected by resistor BI and conductor 68 to the left hand terminal of secondary BI. The burner I3 is grounded at 82 and the lower terminals of condensers 1| and 16 are grounded at 83. A burner flame such as that of a gas pilot burner has a rectifying characteristic in that it has a lower resistance to current flowing in a direction opposite to that of propagation of the flame. Consequently, when there is a flame at pilot burner I3 there is, in effect, a rectifying impedance connected between resistor 8I and ground connections 82 and 83. A photoelectric cell 88 is also connected in parallel with this flame gap. This photoelectric cell comprises an anode 89 and a cathode 98. The anode 88 is connected by conductor SI to the resistor 88. The cathode 88 is connected by conductor 82 to the lower'plates of condensers TI and 16. A photoelectric cell is normally conductive in only one direction and is appreciably conductive in that direction only when illuminated. The photoelectric cell 88 is so mounted The flame responsive device adapted to with respect to the burner flame as to be Illuminated by it. Consequently, when the burner flame is present, the tube 88 likewise functions as a rectifying impedance.

Athird relay is indicated by the reference numeral I88. This relay comprises a relay coil IN and a pluralit of switch blades I82, I83, I84, I85, and I86. Cooperating with the switch blades I82 to I86 are fixed contacts I81, I88, I89, H8, and III. The blades I82, I83, and I88 are biased out of engagement with contacts I81, I88, and III, respectively, and are moved into engagement with those contacts upon cnergization of relay coil I8I. Switch blades I04 and I are biased into engagement with contacts I88 and III, respectively, and are moved out of engagement with those contacts upon energization of the relay coil I8I.

A thermal timer I28 is employed to terminate the operation of the pilot burner, to maintain the blower in operation after the oil valve is closed following a normal operrtion of the burner, and to effect a safety shut down of the burner apparatus in the event of a combustion failure. This timer I28, as shown schematically in the drawing, comprises a bimetallic element I2I which normally engages a contact I22, this contact being the cold contact. Associated with the bimetal element I2I is a heater I23. Upon energization of the heater, the bimetal element I2I warps downwardly into engagement with another fixed contact I24, which may be referred to as the "hot contact."

Connected in series with heater I23 are two series connected resistors I38 and I3I. A switch blade I33 is adapted to engage with either of two contacts I34 or I35, both of which are connected to the series connected resistors I38 and I3I. Contact I34 is connected between resistor I38 and the heater I23 while contact I35 is connected to the junction of resistors I38 and I 3|. Thus, depending upon the position of switch blade I33, it is connected to either the junction of heater I23 and resistor I38 or to the junction of resistors I38 and I3I. As will be pointed out more fully later, the switch blade I33 is employed to control the length of the ignition timing. A resistor I88 is also connected to heater I23 and under certain conditions is in series with it. Power is supplied for operation of relay 25 by a transformer I48. This transformer comprises a primary winding I H and a low voltage secondary winding I42. The primary winding MI is connected by conductors I44, I45, and I46 to two line wires I41 and I48 leading to any suitable source of power (not shown).

A transformer I58 is employed to supply power for the energization of thermal timer heater I23 and for relay I88. The transformer I58 comprises a line voltage primary I5I and a low voltage secondary I52.

The energization of primary I5I is controlled by a thermostat I55, which, like thermostat H, is adapted to respond to the temperature of the oil. This thermostat comprises a bimetallic element I56 carrying a contact I51 adapted to engage with afixed contact I58. Contacts I51 and I58 are maintained out of engagement by bimetallic element I58 as long as the temperature of the oil is below that desirable for operation of the burner. As soon as the action of preheater I5 raises the temperature to the desired operating value, contacts I51 and I58 are closed.

A manually operable switch blade I88 is adapted to be moved into or out of engagement with a fixed contact ISI. Contact I 8| is connected to switch blade I04 while the manually operable switch blade I80 is connected to relay switch blade I03. The position of the switch blade in which it is shown in the drawing is identified by the legend ND which isan abbreviation of No delay. The legend D appears adjacent contact I5I, this legend being an abbreviation of the word Delay." In the position shown, the blower and oil valve are energized simultaneously:' in other words, there is no delay in the energization of the oil. valve after the energization of the blower. With the switch blade I80 in engagement with contact I6I, the blower is energized before the fuelvalve so that there is some delay in the energization of the fuel valve following that of the blower.

1 While the various elements of the apparatus lust described can have a wide range of values, in one particular embodiment, I have found it desirable to employ elements of the following values:

Resistors I30, I3I and I80 had values of 8.8 ohms, 16 ohms, and 18.3 ohms, respectively, The heater I23 had a resistance of 10 ohms. The secondaries I42 and I52 each had output voltages of. 24 volts. In the flame discharge apparatus, each half of secondary 8| had an output of 300 volts and secondary 62 had an output of 12 volts. The size of this secondary winding is, of course, dependent upon the voltage rating of the cathode heater of the tube which is employed for tube 50. In the same embodiment of my invention, I employ condensers of 0.02 microfarad and 0.002 microfarad for condensers l8 and II, respectively. For resistors 10 and I5 I employed resistors having resistance values of 1 and 2 megohms, respectively. I employ a resistor of 3 to 4 megohms for resistor I4 and a resistor of 1 megohm for resistor 8|. As previously indicated, however, it is to be understood that all of these values are merely values employed in a particular embodiment of my invention and that the invention is not in any way limited to the use of elements having these particular values.

Operation Before starting the operation of the system in general, the operation of the flame detecting apparatus will be briefly described.

While the operation of this flame detecting apparatus is briefly set out in the following paragraphs, it is fully set out in the copending application of John M. Wilson, Ser. No. 465,476, flied November 13, 1942, and for a more detailed understanding of the operation of this portion of the apparatus reference is made to that application.

It will be assumed at first that neither the pilot burner nor main burner is ignited. Under these conditions, the only current flowing through condenser 16 is thatfiowing through the following circuit: from the left hand terminal of secondary 6|, through conductors 68 and 69, resistor 10, condenser 1|, conductor I2, condenser 16, resistor I5, and conductor 68 to the center tap of secondary 6|. It will be noted that all of the impedances in this circuit are symmetrically conductive so that the voltage appearing across condenser I8 is an alternating voltage. Furthermore, sincethe lower plate of condenser I6, to which grid 52 is connected, is connected to the opposite terminal of secondary 6 that applied to anode 5|. The effect of this out of phase alternating voltage is to bias grid 52 negatively during the halfcycles in which anode 5| is positive. The tube 50 is therefore non-conductive under these conditions. Now let itbe assumed that a flame exists at pilot burner I8. Under these conditions, a new circuit is established through condenser I8, this circuit being as follows: from the left hand terminal of secondary 8| through conductor 88, resistor 8|, flame electrode 80, the pilot burner flame, pilot burner I8, ground connections 82 and 88, condenser I8, resistor I5, and conductor 68 to the center tap of secondary 8|. The impedance of the pilot burner flame, as pointed out previously,.is rectifying in character. That is, current flows through the pilot flame more readily in the direction traced than in the opposite direction. The efl'ect of current flow through the condenser in the direction traced is to tend to cause the lower plate of condenser 18 to become positive with respect to the upper plate. The grid 52, it will be recalled, is connectedto the lower terminal of condenser 16. Thus, the effect of the current flow through condenser 18 over the circuit just traced, is to raise the potential of the grid 52 in a positive direction with respect to that of cathode 53. The apparatus is so designed that with a normal pilot burner flame, the potential of grid 52 is raised sufliciently that tube 50 becomes sufliciently conductive to effectively energize relay coil 40a. The current flow through relay coil 40a is as follows: from the right hand terminal of secondary 6| through relay coil 40a, conductor 65, anode 5|, cathode 53, and conductors 81 and 88 to the center tap of secondary 8|. The result of the energization of relay coil 40a in this manner is to cause switch blades 40b, 40c, 80d, and Me to move to their energized'positions in which switch blades 40b and 40a are separated from contacts 40 and 40k and switch blades 40c and 40d are moved into engagement with contacts 40gand 40h.

that the tube 88 has the same asymmetrically conductive characteristics as the flame. In'fact, since the tube is almost entirely non-conductive in one direction, it is even more rectifying in character than is the flame. As a result, when- 6| than that to which anode 5| is connected,

ever the photoelectric cell is exposed to the illumination of the main burner flame, the condenser |6 becomes charged in the same manner as when a pilot flame is present.

It is to be pointed out that the electronic apparatus which I employ is responsive only to a rectifying impedance so that if either the flame gap or the terminals of the photoelectric cell are bridged by a non-rectifying impedance, even though it may have the same value of impedance as the flame or the illuminated photoelectric cell, the apparatus will not falsely indicate the presence of a flame.

Turning now to the operation of the apparatus in general, it is assumed that the thermostat I8 is satisfied so that the entire system is shut down. It is also assumed that the oil is above the temperature desired for proper operation of the burner. If the temperature adjacent the bimetallic element I1 of thermostat I 8 now drops.

the arm I8 will be moved. to the left so as to engage first contact I9 and then contact 20.

Nothing happens until both sets of contacts are engaged, at which time a circuit is established to relay coil a as follows: from the righthand terminal of secondary I42 through conductor I15, thermostat contact I9, arm I8, contact 20, conductor I15. contact 40k, switch blade 40c, conductors I11 and I18, heater I23, conductor I18, contact I34, switch blade I33, contact I22, bimetallic element I2I, conductor I8I, switch blade 25c, contact 25s, conductors I82 and -I03, push button switch 39, conductor I04, relay coil 25a. and conductor I85, back to the other terminal of secondary I42. The result of the establishment of this circuit is to cause the energization of relay coil 25a. with the resultant movement of switch blades 25b, 25c, 25d, 25e, 25f, and 25g into their energized positions in which switch blades 25c and 25e are no longer in engagement with contacts 25s and 25t, and in which switch blades 25b, 25c, 25d, 25f, and 259 are in engagement with contacts 2571, 25k, 25m, 2511, and 257),

respectively.

The engagement of switch blade 25d'with con tact 25m results in the establishment of a holding circuit to relay coil 25a as follows: from the right hand terminal of secondary I42 through conductor I15, thermostat contact I9, blade I8, bimetallic element I1, conductor I81, switch blade 25d, contact 25m, conductor I83, push button switch 39, conductor I84, relay coil 25a, and conductor I85 to the left hand terminal of secondary I42. It is to be noted that the holding circuit just traced is independent of contact 20, the last to be engaged of the thermostat contacts. This insures that the relay 25 will remain energized until there has been a rise in temperature suilicient to separate thermostat blade I8 from contact I9.

In this way, provision is made for a diiierential in temperature between the energization and deenergi'zation of relay 25. It is' also to be noted that the holding circuit just traced is independent of the cold contact I22 oi the ther-.

. into operation with relay 40 in its energized position. If it were possible to initiate operation of the system with the relay in this position, there would be no assurance that the relay was not accidentally retained in this position even though flame .were not present. There would thus be no provision for checking the establishment of flame.

The holding circuit for relay 25 also does not include the heater I23. The heater I23 was origit was not broken in any way. Since, as will be more apparentlater, the safety shut down oi the system in the event of flame failure is dependent upon the operation of the thermal timer, it is desirable that the heater be checked before the system is started.

The engagement of switch blade 25b with contact 25h results in the establishment of thefol- 8 sistor I30, conductor I10, heater I23, conductor I19, contact I34, switch blade I33, contact I22, bimetallic element m, and conductor I83 back to the lowerterminal of secondary I52. When switch blade I33 is in engagement with contact I35 insteador contact I34, as shown, the circuit established to heater-I23 upon the engagement of switch blade 25b with contact 2571 is as follows: from the upper terminal of secondary I52 through conductor I80, contact 25h, switch blade 25b, resistor I80, conductor I18, heater I23, conductors I19 and 225, resistor I30, contact I35, switch blade I33, contact I22, bimetallic element I2I, and conductor I88 back to the lower terminal 01' secondary I52. It will be noted that this circuit is identical to the one previously traced except for the fact that it includes resistor I in series with heater I23. The purpose of this is to slow down the heating of the heater and the time required for the bimetallic element I2I of the timer to move from engagement with cold contact I22 into engagement with hot contact I24. Thus, the

The switch I33 is manually moved into engage- ,inally included to-insure that the circuit through -lowing circuit to heater I23, if switch blade I33 is in engagement with contact I34: from the.

upper terminal or secondary I52 through eon ductor I30, contact 25h, switch blade 2511,. -re

ment with one or the other of the two contacts depending upon the length of timing period desired. The resistor I is included in these circuits so as to make the total resistance in series with heater I23 substantially the same as-when the relay coil 25a was in series with-it. .These energizing circuits are effective only if the transformer I50 is energized. The upper terminal of primary I5I of transformer I50 is connected by conductor 20I to the line-wire I58; The lower terminal ofprimary I5I is connected by conductor 202 to the contact I50 of 'oil thermostat I55. For the present, it will be assumed that the operation of the oil preheater is unnecessary and'that the oil is at the desired temperature at which -thermostat contacts I51 and 158 areclosed. Under these conditions, an energizing circuit is established for primary I5 I as'fol10ws:. 'from linewire I41 through conductor 205, bimetallic element I50, contacts I51 and I58, conductor 202, primary I5I, and-conductor 20I to'the other line wire I48. Since, under the conditions assumed, the transformer I50-is energized the establishment of the circuits traced above through heater I23 results in the energizationof that heaterto initiate the timing cycle of the time switch I20. The length of this timing cycle will depend upon whether switch blade I33 is in the short,position shown or in the long positionin which it engages contact I351 The engagement" of relay switch blade 25] with contact 2511. results in the establishment of the following-circuit to the pilot burner gas valve I2:

from line,,wire I41.throug h conductors 205 and -206, contact 2511,- switchblade 25/, conductors means is provided for the pilot burner I3 which ignition means is rendered active along with gas valve I2 so that the'gas admitted to pilot burner I3 by reasoriof the energization of gas valve I2 is ignited. V

' At the same time'as the circuit to gas valve I2 'is. established, a circuit isiestablished to the primary 60 of' transiormer 59 as iollows: from line wire I41, through conductor: I00, switch blade I02, contact I01, conductors I92 and 200, primary 60, and conductors 2 I0, 2 I I, I91, I99, and I45 back to the other line wire I48. After a period or time sufllcient for the tube 50 to become heated, the flame responsive apparatus is in a position to respond to the establishment of a flame at pilot burner I3. This, as previously explained, will cause energization of relay coil 40a with the resultant movement of switch blades 40b, 40c, 40d, and 40a to their energized positions.

The movement of switch blade 40d into engagement with contact 40h results in the establishment of a circuit to the blower motor l as follows: from line wire I41 through conductors I90 and I9I, contact 25p, switch blade 25g, conductors I92 and I93, blower motor I0, conductor I94, switch blade I03, conductors I94 and 2I2, switch blade 40d, contact 407i, and conductors 2| I, I91, I99, and I46'to the other line wire I48.

Simultaneously with the establishment of the circuit just traced to the blower, a circuit is established to oil valve II as follows: from line wire I41,.through conductors 205 and 206, contact 2511,

switch blade 25 conductors 201 and 220, oil valve I I, conductor 22 I, switch blade 40c, contact 409, and conductors 223, 2, I91, I99, and I46 back to the other line wire I48.

As a result of the establishment of the circuits Just traced, both the blower and oil valve are energized simultaneously. This operation has been traced on the assumption that the switch I60 is in the no delay position so that there is no delay in the opening of the fuel oil valve following the energization of the blower. When the switch I60 is in engagement with contact I6I, that is, in the delay position, a circuit is established to it at the same time as one is established to the pilot burner gas valve, this circuit being as follows from line wire I41, through conductors I90 and I9I, contact 25p, relay switch blade 25g, conductors I92 and I93, motor I0, conductor I94, switch blade I60, contact I6I, switch blade I04, contact I09, and conductors I95, I96, I91, I99, and I46 back to the other line wire I48. With the switch in this position, there is a delay between the energization of the blower motor and the opening of the fuel valve equivalent to the time required for the electronic apparatus to warm up and to respond to the presence of a pilot burner flame. It is often desired'to have such an operation of the blower prior to the establishment of fuel flow. It has also been assumed in the operation con-- sidered so far that the oil has been at a temperature at which operation of the preheater I is unnecessary. If the installation is one in which an operation of a, preheater is never necessary, it will be obvious that the lower terminal of primary I 5| of transformer I50 can be connected directly to line wire I41 and that the thermostat 2| and the preheater I5 can be omitted. Where, however, it is necessary to use such a preheater,

' 10 a temperature has been reached at which thermostat I 55 closes its contacts I51 and I58. Shortly above this temperature, the thermostat 2| is satisfled. When thermostat I55 closes its contacts, it is possible for the circuit to timer heater I23 to be established. .During the time that the preheater I5 was warming the oil, this timer heater the timing cycle.

the switch I60 is maintained permanently in the delay position, that is, in engagement with contact I 6I. Thus, upon energization of relay 25, the blower I0 is immediately placed into operation. At the same time, assuming that the thermostat 2| is calling for heating of the oil, a circuit is established to the oil preheater I5 as follows: from line wire I41 through conductors I90 and I9I, contact 251 switch blade 25g, conductor I92, bimetal element 22, contact 23, conductor 240, preheater I5, conductors 24I and I 94, switch blade I60, contact I6I, switch blade I04, contact I09, and conductors I95, I96, I91, I99, and I46 to the other line wire I48. The oil is then heated until I23 has been completely deenergized. While the original thermostat energizing circuit included the timer heater I23, this circuit through timer I23 included contact 25s. As soon as relay 25 became energized, however, the switch blade 25c separated from contact 253 to interrupt this circuit. This is obviously desirable since the oil preheater may require longer to heat up the 011 than is safeto allow for the timing operation of the time switch. With thermostat I satisfied, however, the timer heater I23 is energized to initiate At the same time, th ircuit previously traced to the pilot burner gas valve can be established so that relay 40 can be energized to cause the energization of oil valve I I.

It will be noted that the operation of the preheater requires that the switch I be in continual engagement with contact IBI, in other words, in the delay position. Since the operation of the oil preheater inherently delays the opening of the oil valve a considerable period of time after the operation of the blower, the only action which can possibly be obtained where an oil preheater is used is one in which the opening of the oil valve is delayed after the energization of the blower. Hence, the fact that switch I60 must be in the delay position under these conditions in no way lessens the flexibility of the apparatus.

It will be apparent that regardless of the position of the switch I60, or regardless'ot whether the oil preheater I5 Is used, by the time that the flame responsive device has responded to the presence of the pilot flame and completed the energization of relay 40a, both the oil valve and the blower are in operation. Thus, all of the conditions necessary to the establishment of a-burner flame are present.

At the end of a predetermined period of time following the energization of relay 25, which period of time is determined by the position of switch blade I33 and is normally considerably greater than that required for the operation previously described to take place, the heating effect of the heater I23 on the bimetal element "I has been sufficient to move the element from engagement with contact I22 into engagement with contact I24. This results in the interruption of the previously traced energizing circuit for heater I23.

The heater is maintained energized, however, by

the following circuit: from the upper terminal of secondary I52 through conductor I 86, contact 25h, switch blade 25b, resistor I81, conductor I18, heater I23, conductors I19 and 225, resistors I30 and I3I, conductor 226, contact 25k, relayswitch blade 25c, and conductors I8I and I88 back' to the other terminal of secondary I52. This circuit, while traced for the first time, is established upon energization of relay coil 25b. Due, however, to the fact that it includes resistors I 30 and I3I, one or both of which are shorted out as long as bimetal element I 2| engages contact I22, most of the current flowing through heater I 23 is due to that flowing through the circuit first traced. As soon as the timer moves away from its cold contact I22, however, all of the current must travel through resistors I30 and I3I. This reduces the heating eflect of the thermal timer to in turn reduce the amount of time required for resistors I30 and I3I regardless of the position mal timer I20 into engagement with contact I24 alsoresults in the establishment of an energizing circuit" to relay coil IOI as follows: from the up- I In I the foregoing operation,. it w e s um d per terminal of secondary I52 through conductor 221,. relay coil IOI, conductor 228. contact I24. bimetal element I2I, and conductor I60 to the lower terminal of secondary I52. The establishmentof this circuit causes relay I to be energized with the result that the switch blades I02, I03, I04, I05, and I06 are moved to their energized. positions.

The movement of switch blade I05 out of engagement with contact IIO results in the interruption of the previously traced circuit to the pilot burner gas valve so that the operation of the pilot burner is terminated. This will result in the interruption of the circuit traced through the pilotburner flame and through condenser I0. In the meantime, however, the main urner has presumably been ignited so that the photoelectric cell 86 is now exposed to the main burner flame. As a result, the relay 40 remains energized despite the extinguishment of the pilot burner flame. The operation in the event that the main burner flame has not been established will be discussed in a subsequent paragraph.

The system has now gone through a normal starting cycle and is operating normally. Presumably, it will continue to operate until such time as the thermostat I6 is satisfied; that is, un til the thermostat blade I8 has separated from both contacts I9 and 20. When this happens, the holding circuit for relay is interrupted so that this relay becomes deenergized. As a result, the oil valve is immediately closed. At the same time, the transformer 59 whichsupplies power to the flame detecting apparatus is also deenergized. The energizing circuit to the timer heater I23 is likewise interrupted. Thu the burner flame is extinguished and relay 40 moves to its deenergized position. The blower I0 is maintained in opera-' tion, however, by reason of the following-circuit: from line wire I41 through conductor I; switch blade I02, contact I01, conductors 230 and I03, blower i0, conductor I94, relay switch blade I03,

contact I 08, conductor 230, relay switch blade 253,

contact 25t, and conductors 23I, I93, and I46 to the other line wire I48. As a result of the establishment of the 'circuit'just traced which is dependent upon the de'energization of relay 25 and the energization of relay I00, "the blowermotor continues in operation until the timer. I20 has cooled sufliciently for-blade I2 I to move from engagement with contact I24 into engagement with contact I 22. When this happens'. relay I00 becomes deenergized with the result that switch blade I02 moves out of engagement with contact- I01 to deenergize the blower i0. The apparatus is now all in the starting condition shown in Figure 1.

It will be noted from the above that the blower I0 continued in operation after closure of fuel oil valve I I for a period of time equal to the cooling time of timer I20 to provide blowout operation. As previously explained, this cooling time is reduced by resistors I30 and I3I. As will be noted from the above circuit traced followin the separation of timer switch blade I2I from cold contact I22, the circuit maintained through heater I23 under these conditions includes both of 'switch'blade I33 which, as previously explained. determines whether the ignition timing period .is relatively short or relativelylong. Thus, by

reason of resistors I30 and III, it is possibleto have a "blowout" operation whose length is independent of the ignition timing.

that both th pilot burner and'mai'n' burner ignite normally, as is usually the case. It ,was also assumed that the main burner continued to 0D- erateuntil the thermostat l6 was satisfied. Pro- 'vision'is made with my apparatus to take care. without the inclusion of a separate safety switch,

of contingencies such as the main or pilot burner not-ignitingjor the main burner becoming extinguished during-a-call for heat.

Let it be assumed at first that the pilot bumer I3 didnot originally become ignited. Under these conditions. relay. 40 would never become energized. As a result of this, the oil valve II would never be energized. The thermal timer, however. would continue to heat until the bimetal blade I2I movedfrom engagement with the cold contact into engagement with the hot contact I24. As previouslyexplained, the energization of heater I23 is continued despite the separation of bimetal'blade I2I from contact I22. Also un der these conditions'the relay I00 would becomeenergized by the same-circuit as traced above. This would result in the switch blades I02 to I06 moving to their energized position.- If the selector switch I were in-thejno delay position, the blower I0 is not energ'ize'd'untll the relay 4 0'is energized, Since, under the conditions'ass'umed.

relay 40 has never been energized,.blower III like-' wise has never been energized. The energizetion of relay I00withthe resultant movement of switch blade I05 out of engagement with contact IIO causes deenergization of thep'ilot burner gas valve, previously explained." Thus; all of the burner equipment is deenergizedunder the conditions just considered. The thermal timer is maintained inits hot position and the relay 25 is maintained energized.-

In order to inform the attendant of the failure to start, an alarm'circuit is established under the conditions just considered. This alarm circuit extends from-line wire I" through conductors 205 and206, contact 251:, switch blade 25/, conductors201 and 235, alarm 24, conductor 236, switch blade 4012, contact 40!, conductor 23], relay switch blade I06, contact I I I, and conductors I06, I80, I91, I36, I09, and I46. It will be noted that the above alarm circuit is dependent upon the deenergization of relay 40 and the energizetion of relays 25-and' 'i00. This is the conditionjwhich exists under the conditions just being considered.

"From the 'above, lt will be clear that when the pilot burner isnot initially ignited, the thermal timer which normally operates to time the ignition, and to time the blow out cycle functions to place the apparatus in such a condition that none of the burner equipment is energized and at the 'sametime to sound the alarm to warn the at- ,g'a valvejl2 continue in their energized conditions until the bimetallic element I2I moves into engagement with the hot contact I24. When this happens,- the relay I00 is energized. The ener-' ,13- gization of relay I00, it will be recalled, causes the deenergization .of the pilot burner gas valve I2 so as to extinguish the pilot'burner. Since the main burner has not been ignited, neither the photoelectric cell 90 nor the flame gap provided by electrode 80 is acting as a rectifying impedance so that relay 40 becomes deenerglzed. A condition now exists in which relays 25 and I are energized and relay 40is deenergized. This is the same condition as treated in the previous paragraph. In other words, the blower, the pilot burner gas valve, and the oil valve areall deenergized. The alarm 24 is, however, energized to let the attendant know of the failure to establish combustion.

If main burner combustion is initially estab-' lished but falls during a call for heat. relay 40 becomes deenergized. This again creates a condition in which relays and I00 are energized and relay is deenergized. Again, the blower motor, the pilot burner gas valve, and'the oil valve are deenergized, the alarm being energized.

It will thus be seen that the timer which provides for ignition timing and for a blow out cycle operation of the motor following closure of the fuel oil valve, also functions to place the system in condition where all of the burner apparatus is deenergized. In any of the three cases referred to above, the system will remain shut down until either there is'a power failure, the thermostat ceases to call for heat, or until the push button switch 39 is opened. If there is a power failure, if the thermostat I6 becomes satisfied, or if the push button switch 39 is opened by the attendant after the diillculty has been corrected, the relay 25 will become deenergized. The reclosure of thermostat Iii or of push buttonswitch 39 or the reestablishment of power cannot cause immediate reenergization of relay 25 since the holding circuit established by switch 25d has been opened and it is necessary to again establish the original energizing circuit for relay coil 25 which, it will be recalled, included the cold contact of timer I20. Thus, the system remains shut down until the timer I20 has cooled sufliciently to cause reengagement of bimetallic element I2I with contact I22. When this happens, the entire cycle is repeated, and if the operation of the burner is still not satisfactory, the system will again go "on safety."

In discussing the various contingencies, one possible contingency has been neglected. Where 14 fuel. This has been accomplished without sacriflcing any of the necessary safety features. Furthermore, the system despite the use of the thermal timer for all of the functions named, has a high degree of flexibility and can be used to provide either two lengths of ignition timing, delay the operation of the fuel oil valve following the initiation of blower operation, or simultaneously energize the fuel oil valve and the blower. Furthermore, despite the combined use of the thermal safety switch,'the system is capable of beingutilized where it is necessary to preheat the oil.

I While I have shown a specific embodiment of my invention for purposes of illustration, it is to be understood that the invention is to be limited only by the scope of the appended claims.

I claim as my invention:

1. Burner control apparatus including a fuel control, a burner blower, a burner ignition means. a thermal timer movable from a cold to a hot pwition, a main control switch, means operative as a result of closure of said main switch to cause energization of said burner ignition means, said burner blower, said thermal timer, and said fuel control, means controlled by said thermal timer for interrupting energization of said ignition means upon said timer moving to its hot position, means including said timer operable upon deenergization of said timer and fuel control as a result of opening of said main switch to continue operation of said blower until said timer moves to its cold position, and means operative the operation of the preheater I5 is necessary to bring the oil up to temperature and for some reason the oil preheater is ineffective to bring it up to temperature, the system will continue to operate as far as blower I0 and the oil preheater I5 are concerned. It is necessary to make this operation independent, however, of an thermal safety switch timing since it is often necessary to operate the oil preheater as much as five minutes before the oil reaches the desired temperature. A condition in which the oil preheater I5 does not operate to bring the oil up to temperature is highly unlikely. If it is desired, a V

conventional thermal safety switch can be employed in the motor circuit with the heater of the. safety switch in series with the preheater I 5.

Normally, this precaution is not necessary.

It will be seen from the above that I have provided an improved oil'burner circuit in which provision is made for the use of a timer to not only provide a safety shut down of the system but also to time the ignition and to produce'a timed blow out cycle following the interruption of the upon said main switch being closed and upon a failure of combustion todeenergize said blower and maintain said timer in its hot position.

2. Burner control apparatus including a fuel control, a burner blower, a burner ignition means, a thermal timer movable from a cold to a hot position, a main control switch, means operative as a result of closure of said main switch to cause energization of said burner ignition means, said burner blower, said thermal timer, and said fuel control, means controlled by said thermal timer for interrupting energization of said ignition means upon said timer moving to its hot position, means including said timer operable upon deenergization of said timer and fuel control as a result of opening of said mai switch to continue operation of said blower until said timer moves to its cold position, and means operative upon said main switch being closed and upon a failure of combustion to deenergize said blower immediatelyand to maintain said timer in its hot position under the control of said main switch.

3. Burner control apparatus comprising a fuel control for a burner; a. heater for the fuel; a burner blower; burner ignition means; means including a main control device for initiating operation of said burner ignition means, said fuel perature; means including said fuel temperature responsive device and a device responsive to the operation of the ignition means for energizing said fuel control when said ignition means is operative and said fuel is ata predetermined temperature; and means operative in the event of the burner not being ignited when said timer is at the end of said timing period to cause the operation of said blower, said fuel control, and

. 15 said ignition means to be terminated while maintaining said timer in its hot position.

4. Burner control apparatus for controilng .a burner fuel control. a burner blower and a burner ignition means; said apparatus comprising; first relay adapted to be connected to a main control switch and a source of power so as to be energized when said main control switch is closed; a second relay; means adapted to be associated with a burner and with the ignition means therefor and to energize said second relay when either said ignition means is operative or there is combustion at the burner; a thermal timer having an electrical heater; means for energizing said heater when said first relay is energized; a third relay, means for energizing said third relay when said thermal timer is in its hot poistion; first circuit means controlled by said first and third relays and adapted to be connected to a burner ignition means to energize the latter when said first relay is energized and said third relay is deenergized; second circuit means controlled by said first and second relays and adapted to be connected to a burner fuel control to cause operative energization of the latter when both said first and second relays are energized; third circuit means adapted to be connected to a burner blower and controlled by said first and second relays in such a manner that said blower is maintained in operation when said first relay is energized only if said second relay is also energized so that said blower immediately ceases operation upon said second relay becoming deenergized dueto a combustion failure while said first relay is energized.

5. Burner control apparatus for controlling a burner fuel control, a burner blower and a burner ignition means; said apparatus comprising: a first relay adapted to be connected to a main control switch and a source of power so as to be energized when said main control switch is closed; a second relay; means adapted to be associated with a burner and with the ignition means therefor and to energize said second relay when either said ignition means is operative or there is combustion at the burner; a thermal timer having an electrical heater; means for energizing said heater when said first relay alone is energized; a third relay, means for energizing said third relay when said thermal timer is in its hot position; first circuit means controlled by said first and third relays and adapted to be connected to a burner ignition means to energize the latter when said first relay is energized and said third relay is deenergized; second circuit means controlled by said first and second relays and adapted to be connected to a burner fuel control to cause operative energization of the latter when both said first and second relays are energized; third circuit means adapted to be connected to a burner blower and controlled by said first, second, and third relays in such a manner that said blower is maintained in operation only if said second 7 relay is energized or if said third relay is enersized and said first relay is deenergized so that upon said first relay being deenergized said blower continues in operation until said third relay is deenergized but upon said second relay being deenergized due to a combustion failure, said blower and said fuel control immediately cease operation.

6. Burner control app atus for controlling a burner fuel control, a burner blower and a burner ignition means; said apparatus comprising; a first relay adapted to be connected to a main control switch and a source of power so as to be energized when said main control switch is closed;

a second relay; means adapted to be associated with a burner and with the ignition means therefor and to energize said second relay when either said ignition means is operative or there is combustion at the burner, a thermal timer having an electrical heater; means for energizing said heater when said first relay is energized; a third relay, means for energizing said third relay when said thermal timeris in its hot position; first circuit means controlled by said first and third relays and adapted to be connected to a burner ignition means to energize the latter when said first relay is energized and said third relay is deenergized; second circuit means controlled by said first and second relays and adapted to be connected to a burner fuel control to cause operative energization of the latter when both said first and second relays are energized; third circuit meansadapted to be connected to a burner blower and controlled by said first and second relays in such a manner that said blower is maintained i operation when said first relay is energized only if said second relay is also energized so that said blower immediately ceases operation upon said second relay becoming deenergized due to a combustion failure while said first relay is energized; and fourth circuit means controlled by said second and third relays and adapted to extend to an alarm to energize the same when said third relay is energized and said second relay is deenergized.

7. Burner control apparatus for controlling a burner control and a burner-ignition means; said apparatus comprising: a first relay adapted to be connectedtoa main control switch and a source of power so as to be energized when said main control switch is closed; a second relay; means adapted to be associated with a burner and with the ignition means therefor and to energize said second relay when either said ignition means is operative or there is combustion at the burner, a thermal timer having an electrical heater; means for energizing said heater when said first relay is energized; a third relay; means for energizing said third relay when said thermal timer is in its hot position; first circuit means controlled by said first and third relays and adapted to be connected to a burner ignition means to energize the latter when said first relay is energized and said third relay is'deenergized;

and second circuit means controlled by said first and second relays and adapted to be connected to a burner control to cause operative energization of the latter when both said first and second relays are energized so that said burner control ceases operation and said timer heater remains energized under the control of said first relay when said second relay becomes deenergized due to a combustion failure while said first relay is energized.

8. Burner control apparatus for controlling a burner control and a burner ignition means, said apparatus comprising a first relay adapted to 'gize the latter when said first relay is energized 17 and until said further relay is energized; second circuit means controlled by said first and said further relay and adapted to be connected to a burner control to cause, operative energization of the latter when said first relay is energized and until said further relay is energized; and means adapted to be associated with a. burner and to be effective upon the establishment of combustion at the burner to establish a further energizing circuit meansfor said burner control which is adapted to maintain said burner control energized while said first relay is-energized despite the energization of said further relay.

JOHN D. ROSCHE.

REFERENCES CITED Number UNITED STATES PATENTS Name Date Scott Oct. 5, 1926 McCabe June 19, 1928 Good et-al Apr. 9, 1929 Ray Feb, 17, 1931 Kuempel May 18, 1937 Roy Apr. 12, 1938 R011! Sept. 5, 1939 McGrath Oct. 1, 1940 Tapp et a1. Feb. 4, 1941 Bock Dec. 23, 1941 Bulger Feb. 13, 1945 Gille July 10, 1945 

